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C++: namespaces and scopes for enum values (PR c++/88121)

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Consider this test case:

namespace json
{
  enum { JSON_OBJECT };
}

void test ()
{
  JSON_OBJECT;
}

which erroneously accesses an enum value in another namespace without
qualifying the access.

GCC 6 through 8 issue a suggestion that doesn't mention the namespace:

<source>: In function 'void test()':
<source>:8:3: error: 'JSON_OBJECT' was not declared in this scope
   JSON_OBJECT;
   ^~~~~~~~~~~
<source>:8:3: note: suggested alternative:
<source>:3:10: note:   'JSON_OBJECT'
   enum { JSON_OBJECT };
          ^~~~~~~~~~~

which is suboptimal.

I made the problem worse with r265610, which consolidates the single
suggestion into the error, and emits:

<source>: In function 'void test()':
<source>:8:3: error: 'JSON_OBJECT' was not declared in this scope; did
   you mean 'JSON_OBJECT'?
    8 |   JSON_OBJECT;
      |   ^~~~~~~~~~~
      |   JSON_OBJECT
<source>:3:10: note: 'JSON_OBJECT' declared here
    3 |   enum { JSON_OBJECT };
      |          ^~~~~~~~~~~

where the message:
  'JSON_OBJECT' was not declared in this scope; did you mean 'JSON_OBJECT'?
is nonsensical.

This patch tweaks dump_scope to detect unscoped enums, and to use the
enclosing namespace for them, so that the CONST_DECL is dumped as
"json::JSON_OBJECT".

This changes the output for the above so that it refers to the
namespace, fixing the issue:

<source>:8:3: error: 'JSON_OBJECT' was not declared in this scope; did
   you mean 'json::JSON_OBJECT'?
    9 |   JSON_OBJECT;
      |   ^~~~~~~~~~~
      |   json::JSON_OBJECT
<source>3:10: note: 'json::JSON_OBJECT' declared here
    3 |   enum { JSON_OBJECT };
      |          ^~~~~~~~~~~

The patch also fixes scope-printing for values within scoped enums.
To exercise this, the patch extends the scanner for namespaces for
exact matches for a name, so that we also scan inside scoped
enums, to cover the case where someone doesn't supply the scope.

Hence with the patch given e.g.:

enum class vegetable { CARROT, TURNIP };

we're able to offer e.g.:

suggestions-scoped-enums.C:50:3: error: 'CARROT' was not declared in
  this scope; did you mean 'vegetable::CARROT'?
   50 |   CARROT;
      |   ^~~~~~
      |   vegetable::CARROT

and this exercises the code path above.  The patch updates dump_scope
for scoped enums so that we print the scope when printing the
value ("vegetable::CARROT"), rather than just the name of the value
("CARROT").

Finally, the patch adds spell-corrections within a scoped enum,
giving e.g.:

suggestions-scoped-enums.C:18:14: error: 'TURNUP' is not a member of
  'vegetable'; did you mean 'TURNIP'?
   18 |   vegetable::TURNUP;
      |              ^~~~~~
      |              TURNIP

gcc/cp/ChangeLog:
	PR c++/88121
	* cp-name-hint.h (suggest_alternative_in_scoped_enum): New decl.
	* error.c (dump_scope): Ensure that we print any scope for values
	of unscoped enums.  Print the scope of values of scoped enums.
	(qualified_name_lookup_error): Offer suggestions for failures
	within scoped enums by calling suggest_alternative_in_scoped_enum.
	* name-lookup.c (class namespace_hints): Update comment to mention
	scoped enums.
	(namespace_hints::namespace_hints): Call
	maybe_add_candidate_for_scoped_enum.
	(namespace_hints::maybe_add_candidate_for_scoped_enum): New member
	(suggest_alternatives_for): Update comment to mention scoped
	enums.
	(suggest_alternative_in_scoped_enum): New function.

gcc/testsuite/ChangeLog:
	PR c++/88121
	* g++.dg/lookup/suggestions-scoped-enums.C: New test.
	* g++.dg/lookup/suggestions-unscoped-enums.C: New test.

From-SVN: r266644
This commit is contained in:
David Malcolm 2018-11-29 21:21:56 +00:00 committed by David Malcolm
parent 171954d816
commit 3ded6ffdfd
7 changed files with 310 additions and 12 deletions

17
gcc/cp/ChangeLog

@ -1,3 +1,20 @@
2018-11-29 David Malcolm <dmalcolm@redhat.com>
PR c++/88121
* cp-name-hint.h (suggest_alternative_in_scoped_enum): New decl.
* error.c (dump_scope): Ensure that we print any scope for values
of unscoped enums. Print the scope of values of scoped enums.
(qualified_name_lookup_error): Offer suggestions for failures
within scoped enums by calling suggest_alternative_in_scoped_enum.
* name-lookup.c (class namespace_hints): Update comment to mention
scoped enums.
(namespace_hints::namespace_hints): Call
maybe_add_candidate_for_scoped_enum.
(namespace_hints::maybe_add_candidate_for_scoped_enum): New member
(suggest_alternatives_for): Update comment to mention scoped
enums.
(suggest_alternative_in_scoped_enum): New function.
2018-11-28 Marek Polacek <polacek@redhat.com>
Implement P1094R2, Nested inline namespaces.

1
gcc/cp/cp-name-hint.h

@ -33,5 +33,6 @@ along with GCC; see the file COPYING3. If not see
extern name_hint suggest_alternatives_for (location_t, tree, bool);
extern name_hint suggest_alternatives_in_other_namespaces (location_t, tree);
extern name_hint suggest_alternative_in_explicit_scope (location_t, tree, tree);
extern name_hint suggest_alternative_in_scoped_enum (tree, tree);
#endif /* GCC_CP_NAME_HINT_H */

25
gcc/cp/error.c

@ -182,6 +182,12 @@ dump_scope (cxx_pretty_printer *pp, tree scope, int flags)
if (scope == NULL_TREE)
return;
/* Enum values within an unscoped enum will be CONST_DECL with an
ENUMERAL_TYPE as their "scope". Use CP_TYPE_CONTEXT of the
ENUMERAL_TYPE, so as to print any enclosing namespace. */
if (UNSCOPED_ENUM_P (scope))
scope = CP_TYPE_CONTEXT (scope);
if (TREE_CODE (scope) == NAMESPACE_DECL)
{
if (scope != global_namespace)
@ -190,7 +196,8 @@ dump_scope (cxx_pretty_printer *pp, tree scope, int flags)
pp_cxx_colon_colon (pp);
}
}
else if (AGGREGATE_TYPE_P (scope))
else if (AGGREGATE_TYPE_P (scope)
|| SCOPED_ENUM_P (scope))
{
dump_type (pp, scope, f);
pp_cxx_colon_colon (pp);
@ -4261,7 +4268,21 @@ qualified_name_lookup_error (tree scope, tree name,
print_candidates (decl);
}
else
error_at (location, "%qD is not a member of %qT", name, scope);
{
name_hint hint;
if (SCOPED_ENUM_P (scope))
hint = suggest_alternative_in_scoped_enum (name, scope);
if (const char *suggestion = hint.suggestion ())
{
gcc_rich_location richloc (location);
richloc.add_fixit_replace (suggestion);
error_at (&richloc,
"%qD is not a member of %qT; did you mean %qs?",
name, scope, suggestion);
}
else
error_at (location, "%qD is not a member of %qT", name, scope);
}
}
else if (scope != global_namespace)
{

72
gcc/cp/name-lookup.c

@ -5396,8 +5396,8 @@ class suggest_alternatives : public deferred_diagnostic
};
/* A class for encapsulating the result of a search across
multiple namespaces for an unrecognized name seen at a
given source location. */
multiple namespaces (and scoped enums within them) for an
unrecognized name seen at a given source location. */
class namespace_hints
{
@ -5408,6 +5408,8 @@ class namespace_hints
name_hint maybe_decorate_with_limit (name_hint);
private:
void maybe_add_candidate_for_scoped_enum (tree scoped_enum, tree name);
location_t m_loc;
tree m_name;
vec<tree> m_candidates;
@ -5419,8 +5421,8 @@ class namespace_hints
bool m_limited;
};
/* Constructor for namespace_hints. Search namespaces, looking for a match
for unrecognized NAME seen at LOC. */
/* Constructor for namespace_hints. Search namespaces and scoped enums,
looking for an exact match for unrecognized NAME seen at LOC. */
namespace_hints::namespace_hints (location_t loc, tree name)
: m_loc(loc), m_name (name)
@ -5451,10 +5453,22 @@ namespace_hints::namespace_hints (location_t loc, tree name)
for (tree decl = NAMESPACE_LEVEL (ns)->names;
decl; decl = TREE_CHAIN (decl))
if (TREE_CODE (decl) == NAMESPACE_DECL
&& !DECL_NAMESPACE_ALIAS (decl)
&& !DECL_NAMESPACE_INLINE_P (decl))
children.safe_push (decl);
{
if (TREE_CODE (decl) == NAMESPACE_DECL
&& !DECL_NAMESPACE_ALIAS (decl)
&& !DECL_NAMESPACE_INLINE_P (decl))
children.safe_push (decl);
/* Look for exact matches for NAME within scoped enums.
These aren't added to the worklist, and so don't count
against the search limit. */
if (TREE_CODE (decl) == TYPE_DECL)
{
tree type = TREE_TYPE (decl);
if (SCOPED_ENUM_P (type))
maybe_add_candidate_for_scoped_enum (type, name);
}
}
while (!m_limited && !children.is_empty ())
{
@ -5522,11 +5536,32 @@ namespace_hints::maybe_decorate_with_limit (name_hint hint)
return hint;
}
/* Look inside SCOPED_ENUM for exact matches for NAME.
If one is found, add its CONST_DECL to m_candidates. */
void
namespace_hints::maybe_add_candidate_for_scoped_enum (tree scoped_enum,
tree name)
{
gcc_assert (SCOPED_ENUM_P (scoped_enum));
for (tree iter = TYPE_VALUES (scoped_enum); iter; iter = TREE_CHAIN (iter))
{
tree id = TREE_PURPOSE (iter);
if (id == name)
{
m_candidates.safe_push (TREE_VALUE (iter));
return;
}
}
}
/* Generate a name_hint at LOCATION for NAME, an IDENTIFIER_NODE for which
name lookup failed.
Search through all available namespaces and generate a suggestion and/or
a deferred diagnostic that lists possible candidate(s).
Search through all available namespaces and any scoped enums within them
and generate a suggestion and/or a deferred diagnostic that lists possible
candidate(s).
If no exact matches are found, and SUGGEST_MISSPELLINGS is true, then also
look for near-matches and suggest the best near-match, if there is one.
@ -5910,6 +5945,23 @@ suggest_alternative_in_explicit_scope (location_t location, tree name,
return name_hint ();
}
/* Given NAME, look within SCOPED_ENUM for possible spell-correction
candidates. */
name_hint
suggest_alternative_in_scoped_enum (tree name, tree scoped_enum)
{
gcc_assert (SCOPED_ENUM_P (scoped_enum));
best_match <tree, const char *> bm (name);
for (tree iter = TYPE_VALUES (scoped_enum); iter; iter = TREE_CHAIN (iter))
{
tree id = TREE_PURPOSE (iter);
bm.consider (IDENTIFIER_POINTER (id));
}
return name_hint (bm.get_best_meaningful_candidate (), NULL);
}
/* Look up NAME (an IDENTIFIER_NODE) in SCOPE (either a NAMESPACE_DECL
or a class TYPE).

6
gcc/testsuite/ChangeLog

@ -1,3 +1,9 @@
2018-11-29 David Malcolm <dmalcolm@redhat.com>
PR c++/88121
* g++.dg/lookup/suggestions-scoped-enums.C: New test.
* g++.dg/lookup/suggestions-unscoped-enums.C: New test.
2018-11-29 Peter Bergner <bergner@linux.ibm.com>
PR target/87496

110
gcc/testsuite/g++.dg/lookup/suggestions-scoped-enums.C Normal file

@ -0,0 +1,110 @@
// { dg-do compile { target c++11 } }
// { dg-options "-fdiagnostics-show-caret" }
/* Verify that we offer suggestions for misspelled values
in scoped enums, and for values from scoped enums that
are missing their scope.
Verify that we emit fix-it hints for those cases for
which we have adequate location information. */
enum class vegetable { CARROT, TURNIP }; // { dg-line decl_of_vegetable }
namespace pasta
{
enum class shape { LASAGNA, LINGUINE, SPAGHETTI, TAGLIATELLE }; // { dg-line decl_of_shape }
}
void misspelled_value_in_scoped_enum ()
{
vegetable::TURNUP; // { dg-error "'TURNUP' is not a member of 'vegetable'; did you mean 'TURNIP'" }
/* { dg-begin-multiline-output "" }
vegetable::TURNUP;
^~~~~~
TURNIP
{ dg-end-multiline-output "" } */
}
void misspelled_value_using_explicit_ns ()
{
pasta::shape::SPOOGHETTI; // { dg-error "'SPOOGHETTI' is not a member of 'pasta::shape'; did you mean 'SPAGHETTI'" }
/* { dg-begin-multiline-output "" }
pasta::shape::SPOOGHETTI;
^~~~~~~~~~
SPAGHETTI
{ dg-end-multiline-output "" } */
}
namespace pasta {
void misspelled_value_using_implicit_ns ()
{
shape::SPOOGHETTI; // { dg-error "'SPOOGHETTI' is not a member of 'pasta::shape'; did you mean 'SPAGHETTI'" }
/* { dg-begin-multiline-output "" }
shape::SPOOGHETTI;
^~~~~~~~~~
SPAGHETTI
{ dg-end-multiline-output "" } */
}
} // namespace pasta
void unqualified_enum_in_global_ns ()
{
CARROT; // { dg-error "'CARROT' was not declared in this scope; did you mean 'vegetable::CARROT'" }
/* { dg-begin-multiline-output "" }
CARROT;
^~~~~~
vegetable::CARROT
{ dg-end-multiline-output "" } */
// { dg-message "'vegetable::CARROT' declared here" "" { target *-*-* } decl_of_vegetable }
/* { dg-begin-multiline-output "" }
enum class vegetable { CARROT, TURNIP };
^~~~~~
{ dg-end-multiline-output "" } */
}
void unqualified_enum_in_ns ()
{
LASAGNA; // { dg-error "'LASAGNA' was not declared in this scope; did you mean 'pasta::shape::LASAGNA'" }
/* { dg-begin-multiline-output "" }
LASAGNA;
^~~~~~~
pasta::shape::LASAGNA
{ dg-end-multiline-output "" } */
// { dg-message "'pasta::shape::LASAGNA' declared here" "" { target *-*-* } decl_of_shape }
/* { dg-begin-multiline-output "" }
enum class shape { LASAGNA, LINGUINE, SPAGHETTI, TAGLIATELLE };
^~~~~~~
{ dg-end-multiline-output "" } */
}
/* We can't guarantee location information here, so don't expect a
fix-it hint. */
void unqualified_enum_in_explicit_ns ()
{
pasta::LINGUINE; // { dg-error "'LINGUINE' is not a member of 'pasta'; did you mean 'pasta::shape::LINGUINE'" }
/* { dg-begin-multiline-output "" }
pasta::LINGUINE;
^~~~~~~~
{ dg-end-multiline-output "" } */
// { dg-message "'pasta::shape::LINGUINE' declared here" "" { target *-*-* } decl_of_shape }
/* { dg-begin-multiline-output "" }
enum class shape { LASAGNA, LINGUINE, SPAGHETTI, TAGLIATELLE };
^~~~~~~~
{ dg-end-multiline-output "" } */
}
namespace pasta {
void unqualified_enum_in_implicit_ns ()
{
TAGLIATELLE; // { dg-error "'TAGLIATELLE' was not declared in this scope; did you mean 'pasta::shape::TAGLIATELLE'" }
/* { dg-begin-multiline-output "" }
TAGLIATELLE;
^~~~~~~~~~~
pasta::shape::TAGLIATELLE
{ dg-end-multiline-output "" } */
// { dg-message "'pasta::shape::TAGLIATELLE' declared here" "" { target *-*-* } decl_of_shape }
/* { dg-begin-multiline-output "" }
enum class shape { LASAGNA, LINGUINE, SPAGHETTI, TAGLIATELLE };
^~~~~~~~~~~
{ dg-end-multiline-output "" } */
}
}

91
gcc/testsuite/g++.dg/lookup/suggestions-unscoped-enums.C Normal file

@ -0,0 +1,91 @@
// { dg-options "-fdiagnostics-show-caret" }
enum { LASAGNA, SPAGHETTI };
namespace outer_ns_a
{
enum enum_in_outer_ns_a { STRAWBERRY, BANANA };
namespace inner_ns
{
enum enum_in_inner_ns { ELEPHANT, LION };
}
}
namespace outer_ns_b
{
enum enum_in_outer_ns_b { NIGHT, DAY };
}
void misspelled_enum_in_global_ns ()
{
SPOOGHETTI; // { dg-error "'SPOOGHETTI' was not declared in this scope; did you mean 'SPAGHETTI'" }
/* { dg-begin-multiline-output "" }
SPOOGHETTI;
^~~~~~~~~~
SPAGHETTI
{ dg-end-multiline-output "" } */
}
void unqualified_enum_in_outer_ns ()
{
BANANA; // { dg-error "'BANANA' was not declared in this scope; did you mean 'outer_ns_a::BANANA'" }
/* { dg-begin-multiline-output "" }
BANANA;
^~~~~~
outer_ns_a::BANANA
{ dg-end-multiline-output "" } */
/* { dg-begin-multiline-output "" }
enum enum_in_outer_ns_a { STRAWBERRY, BANANA };
^~~~~~
{ dg-end-multiline-output "" } */
}
namespace outer_ns_a
{
void misspelled_unqualified_enum_in_outer_ns () {
BANANAS; // { dg-error "'BANANAS' was not declared in this scope; did you mean 'BANANA'" }
/* { dg-begin-multiline-output "" }
BANANAS;
^~~~~~~
BANANA
{ dg-end-multiline-output "" } */
}
};
void unqualified_enum_in_inner_ns ()
{
ELEPHANT; // { dg-error "'ELEPHANT' was not declared in this scope; did you mean 'outer_ns_a::inner_ns::ELEPHANT'" }
/* { dg-begin-multiline-output "" }
ELEPHANT;
^~~~~~~~
outer_ns_a::inner_ns::ELEPHANT
{ dg-end-multiline-output "" } */
/* { dg-begin-multiline-output "" }
enum enum_in_inner_ns { ELEPHANT, LION };
^~~~~~~~
{ dg-end-multiline-output "" } */
}
void partially_qualified_enum_in_inner_ns ()
{
outer_ns_a::ELEPHANT; // { dg-error "'ELEPHANT' is not a member of 'outer_ns_a'; did you mean 'outer_ns_a::inner_ns::ELEPHANT'" }
/* { dg-begin-multiline-output "" }
outer_ns_a::ELEPHANT;
^~~~~~~~
{ dg-end-multiline-output "" } */
/* { dg-begin-multiline-output "" }
enum enum_in_inner_ns { ELEPHANT, LION };
^~~~~~~~
{ dg-end-multiline-output "" } */
}
void wrongly_qualified_enum ()
{
outer_ns_a::NIGHT; // { dg-error "'NIGHT' is not a member of 'outer_ns_a'; did you mean 'outer_ns_b::NIGHT'" }
/* { dg-begin-multiline-output "" }
outer_ns_a::NIGHT;
^~~~~
{ dg-end-multiline-output "" } */
/* { dg-begin-multiline-output "" }
enum enum_in_outer_ns_b { NIGHT, DAY };
^~~~~
{ dg-end-multiline-output "" } */
}